This invention relates generally to gas turbine engines, and more specifically to methods and apparatus for balancing an assembly that includes a gas turbine engine.
At least some known gas turbine engines include, in serial flow arrangement, a compressor, a combustor, a high pressure turbine, and a low pressure turbine. The compressor, combustor and high pressure turbine are sometimes collectively referred to as the gas generator or core engine. Compressed air is channeled from the compressor to the combustor where it is mixed with fuel and ignited. The combustion gasses are channeled to the turbines which extract energy from the combustion gasses to power the compressors and to produce useful work to propel an aircraft in flight or to power a load, such as an electrical generator.
Balancing turbine engines facilitates the avoidance of potentially destructive vibrational forces during engine operation. Balancing is achieved by rotating the assembly and determining the magnitude and location of each imbalance. Material is then added or removed to correct the unbalance. Generally, the rotating components are balanced individually, and after the components are assembled, the assembly is then balanced to correct for any cumulative unbalance in the assembly. Within at least some applications, the low pressure turbine or power turbine is coupled to other rotating components that necessitate further balancing.
Within at least some known engine assemblies, the power turbine, is coupled to a generator. When the engine is installed in a vessel, it is desirable that the engine and generator be field balanced as installed to facilitate preventing the generation of potentially damaging vibrational forces being induced to the surrounding vessel. At least some known engines are balance utilizing a plurality of balance weights. In use, at least one balance weight is coupled to the engine to facilitate reducing the vibrational forces on the surrounding vessel, whereas some engines may require a significant amount of unbalance correction. Therefore, an additional quantity of weights are coupled to the engine. However, coupling a plurality of balance weights to the engine results in a relatively time consuming process. Specifically, each respective weight must be attached to a respective bolt. Accordingly, when the engine requires a significant amount of unbalance correction, there may be an insufficient quantity of bolts available for weight attachment.